This invention relates to quick coupler devices for fluid systems, and more particularly, to a rigid mount, breakaway, quick coupler having a flow-check feature therein.
Similar devices of this type are well known in the art, however, there are disadvantages with most of these because of the mode of operation and the varied applications which the coupler encounters. Some of the prior art devices are directed to the agricultural environment wherein the coupler is mounted on a tractor for receiving fluid from the control valve of the tractor and for coupling with the hose nipple of a hydraulic implement to be actuated by the fluid power source. Often this implement is a closed fluid system so that the nipple is presented to the coupler under fluid pressure. In this event, the accommodation must be made for the different mechanical interconnection which occurs and the subsequent opening of the closed fluid valve of the nipple to a full open flow condition.
Most of the couplers of this type which rely on a spring to hold the nipple valve open are subject to an undesirable characteristic called flow-checking. Flow-checking occurs when a surge of oil moves from nipple to coupler with sufficient force to overcome the coupler valve spring and allow the nipple valve to close and check the flow of oil. Mechanically actuated stops have been provided in the past to prevent flow-checking and the instant invention is an improvement in this type of device.
One example of prior art valve is shown in U.S. Pat. No. 4,200,121 wherein a mechanical stop is provided to produce the flow-checking feature. The stop is in the form of a pin which is spring loaded in the direction of its locking position and which cooperates with the stem of the coupler valve support member to control the flow-check movement of the coupler valve. A sleeve is provided on the stem and is axially movable relative thereto for resetting the stop pin by means of a ramp surface on one edge of the sleeve. Resetting of the coupler occurs upon disengagement of the nipple and leaves it in a position of preparedness for the next engagement cycle. A second embodiment of coupler is described in this patent wherein a flow responsive vane provides rotary movement, against the action of a torsion spring, to actuate a detent cam for locking cooperation with the detent contour of the valve support stem.
Another prior art device is manufactured by the assignee of the above-noted patent, also employing a mechanical stop to prevent flow-checking. This stop is in the form of a hairpin spring in a right angle bend, where the legs of the pin straddle the valve stem under control of a shiftable sleeve and are spread by a ramp surface for resetting purposes.
A problem with the latter design is that the stop device is not actuated if the connecting nipple is not under pressure. In this instance the valve stem moves back only a short distance and does not cause shifting of the sleeve relative to the valve stem. Consequently, the nipple can flow-check. However, when flow-checking does occur, the coupler valve stem will move the full required distance wherein the sleeve separates from a shoulder on the stem and allows the stop to engage to prevent further flow-checking.
A still further form of prior art structure is shown in U.S. Pat. No. 4,398,561 wherein a mechanical stop cooperates with the coupler valve support stem to provide flow-checking. In this arrangement, however, the stop is activated by the flow of fluid through the coupler whereby a sleeve is moved to force locking balls into engagement with the stem. This type of design is subject to flow conditions and is dependent to some extent upon fluid viscosity and the like.